The endotelial and vein wall reaction on pulsatile flow and shear stress from arterial ‘jets’ originating from arterioVenous anastomoses (AVAs) studied by scanning electron microscopy (SEM)

2006 ◽  
Vol 39 ◽  
pp. S282
Author(s):  
L. Schalin ◽  
D. Liepsch
Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 114-114
Author(s):  
Alessandro Zarpellon ◽  
Patrizia Marchese ◽  
Antonella Zampolli ◽  
Grazia Loredana Mendolicchio ◽  
Zaverio M. Ruggeri

Abstract Generation of α-thrombin (FIIa) in response to vascular injury is a key mechanism influencing thrombus formation. Platelet activation by FIIa is mediated by different protease activated receptors (PARs), although the most abundant FIIa binding site on platelets, but not a substrate for proteolysis, is glycoprotein (GP) Ibα in the GPIb-IX-V complex. The functional role of GPIbα in mediating/regulation thrombin functions relative to that of different PARs remains unclear. The goal of these studies was to define how binding to GPIbα can modulate FIIa functions. In mouse platelets we replaced endogenous GPIbα with either its human wild type counterpart (huGPIbα-WT) or with huGPIbα mutated at key residues involved in thrombin binding (D277N, Y276-8-9/F). Because these two mutations resulted in an undistinguishable phenotype, they are designated collectively as huGPIbα-Mut hereon. Mice expressing huGPIbα, WT or Mut, were evaluated in intravital models of arterial thrombosis induced by a ferric chloride-induced carotid artery lesion and venous thromboembolism induced by intravenous α-thrombin injection. Moreover, the blood of huGPIbα WT or Mut mice was also tested in an ex vivo model of thrombus formation upon perfusion over a thrombogenic surface under controlled flow conditions and platelets were evaluated for their responses to FIIa-induced activation. Mice expressing huGPIbα - WT or Mut - have comparable platelet counts and GPIbα surface density. Moreover, huGPIbα-WT platelets bind FIIa similarly than their normal human control counterpart, while huGPIbα-Mut platelets have essentially no detectable FIIa binding. Upon FIIa stimulation, which on mouse platelets is mediated by PAR4, aggregation and Ca2+ transients were significantly enhanced in huGPIbα-Mut as compared to huGPIbα-WT. In contrast, blocking FIIa binding to GPIbα on human platelets essentially abolished FIIa mediated activation, which in human occurs predominantly through PAR1. These results are compatible with the conclusion that, in mice, GPIbα is a competitive inhibitor of FIIa for PAR4-mediated functions. In the presence of metabolically inactive (PGE1 treated) huGPIbα-Mut washed platelets, the clotting time of a purified fibrinogen solution was significantly shorter when triggered by relative high concentration of FIIa (4 nM), but pronouncedly prolonged at a lower FIIa concentration (0.5 nM). Clot visualization showed a much more structured fibrin mesh in the presence of huGPIbα-WT platelets, which was lost with in the presence of huGPIbα-Mut platelets. Mutant mice tested in a model of carotid artery injury exhibited a pronounced prothrombotic phenotype, with a shorter time to occlusion. However they were protected from death induced by I.V. injection of α-thrombin. In ex vivo perfusion studies, the total volume of platelet aggregates formed in huGPIbα-Mut mouse blood exposed to acid-insoluble fibrillar collagen type I was slightly bigger than in huGPIbα-WT mice, but the number of thrombi was increased and their individual size smaller. These huGPIbα-Mut platelets exhibited clear signs of increased activation, as visualized by scanning electron microscopy (SEM). Strikingly, fibrin was almost totally absent in the huGPIbα-Mut thrombi. This was in striking contrast with what observed in huGPIbα-WT mice, in which the surface of platelet thrombi with directly and tightly connected with thick fibrin fibers as visualized by scanning electron microscopy. Possibly because of the reduced platelet membrane-fibrin fibril connection in huGPIbα-Mut platelets, these mice were significantly less susceptible to death when injected with an α-thrombin dose that caused 80% mortality plus in huGPIbα-WT mice. Thus, mice whose platelets have defective α-thrombin binding to GPIbα have a prothrombotic phenotype in high shear stress flow arteries and are protected from thromboembolic death in the low shear stress venous circulation. Our findings identify GPIbα as a relevant FIIa activity modulator in hemostasis and thrombosis through distinct and opposite mechanisms affecting platelet activation (The Yin) and fibrin formation (The Yang). Disclosures No relevant conflicts of interest to declare.


Author(s):  
P.S. Porter ◽  
T. Aoyagi ◽  
R. Matta

Using standard techniques of scanning electron microscopy (SEM), over 1000 human hair defects have been studied. In several of the defects, the pathogenesis of the abnormality has been clarified using these techniques. It is the purpose of this paper to present several distinct morphologic abnormalities of hair and to discuss their pathogenesis as elucidated through techniques of scanning electron microscopy.


Author(s):  
P.J. Dailey

The structure of insect salivary glands has been extensively investigated during the past decade; however, none have attempted scanning electron microscopy (SEM) in ultrastructural examinations of these secretory organs. This study correlates fine structure by means of SEM cryofractography with that of thin-sectioned epoxy embedded material observed by means of transmission electron microscopy (TEM).Salivary glands of Gromphadorhina portentosa were excised and immediately submerged in cold (4°C) paraformaldehyde-glutaraldehyde fixative1 for 2 hr, washed and post-fixed in 1 per cent 0s04 in phosphosphate buffer (4°C for 2 hr). After ethanolic dehydration half of the samples were embedded in Epon 812 for TEM and half cryofractured and subsequently critical point dried for SEM. Dried specimens were mounted on aluminum stubs and coated with approximately 150 Å of gold in a cold sputtering apparatus.Figure 1 shows a cryofractured plane through a salivary acinus revealing topographical relief of secretory vesicles.


Author(s):  
Nakazo Watari ◽  
Yasuaki Hotta ◽  
Yoshio Mabuchi

It is very useful if we can observe the identical cell elements within the same sections by light microscopy (LM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM) sequentially, because, the cell fine structure can not be indicated by LM, while the color is; on the other hand, the cell fine structure can be very easily observed by EM, although its color properties may not. However, there is one problem in that LM requires thick sections of over 1 μm, while EM needs very thin sections of under 100 nm. Recently, we have developed a new method to observe the same cell elements within the same plastic sections using both light and transmission (conventional or high-voltage) electron microscopes.In this paper, we have developed two new observation methods for the identical cell elements within the same sections, both plastic-embedded and paraffin-embedded, using light microscopy, transmission electron microscopy and/or scanning electron microscopy (Fig. 1).


Author(s):  
Ronald H. Bradley ◽  
R. S. Berk ◽  
L. D. Hazlett

The nude mouse is a hairless mutant (homozygous for the mutation nude, nu/nu), which is born lacking a thymus and possesses a severe defect in cellular immunity. Spontaneous unilateral cataractous lesions were noted (during ocular examination using a stereomicroscope at 40X) in 14 of a series of 60 animals (20%). This transmission and scanning microscopic study characterizes the morphology of this cataract and contrasts these data with normal nude mouse lens.All animals were sacrificed by an ether overdose. Eyes were enucleated and immersed in a mixed fixative (1% osmium tetroxide and 6% glutaraldehyde in Sorenson's phosphate buffer pH 7.4 at 0-4°C) for 3 hours, dehydrated in graded ethanols and embedded in Epon-Araldite for transmission microscopy. Specimens for scanning electron microscopy were fixed similarly, dehydrated in graded ethanols, then to graded changes of Freon 113 and ethanol to 100% Freon 113 and critically point dried in a Bomar critical point dryer using Freon 13 as the transition fluid.


Author(s):  
Jane A. Westfall ◽  
S. Yamataka ◽  
Paul D. Enos

Scanning electron microscopy (SEM) provides three dimensional details of external surface structures and supplements ultrastructural information provided by transmission electron microscopy (TEM). Animals composed of watery jellylike tissues such as hydras and other coelenterates have not been considered suitable for SEM studies because of the difficulty in preserving such organisms in a normal state. This study demonstrates 1) the successful use of SEM on such tissue, and 2) the unique arrangement of batteries of nematocysts within large epitheliomuscular cells on tentacles of Hydra littoralis.Whole specimens of Hydra were prepared for SEM (Figs. 1 and 2) by the fix, freeze-dry, coat technique of Small and Màrszalek. The specimens were fixed in osmium tetroxide and mercuric chloride, freeze-dried in vacuo on a prechilled 1 Kg brass block, and coated with gold-palladium. Tissues for TEM (Figs. 3 and 4) were fixed in glutaraldehyde followed by osmium tetroxide. Scanning micrographs were taken on a Cambridge Stereoscan Mark II A microscope at 10 KV and transmission micrographs were taken on an RCA EMU 3G microscope (Fig. 3) or on a Hitachi HU 11B microscope (Fig. 4).


Author(s):  
J.N. Ramsey ◽  
D.P. Cameron ◽  
F.W. Schneider

As computer components become smaller the analytical methods used to examine them and the material handling techniques must become more sensitive, and more sophisticated. We have used microbulldozing and microchiseling in conjunction with scanning electron microscopy, replica electron microscopy, and microprobe analysis for studying actual and potential problems with developmental and pilot line devices. Foreign matter, corrosion, etc, in specific locations are mechanically loosened from their substrates and removed by “extraction replication,” and examined in the appropriate instrument. The mechanical loosening is done in a controlled manner by using a microhardness tester—we use the attachment designed for our Reichert metallograph. The working tool is a pyramid shaped diamond (a Knoop indenter) which can be pushed into the specimen with a controlled pressure and in a specific location.


Author(s):  
Yasushi Kokubo ◽  
Hirotami Koike ◽  
Teruo Someya

One of the advantages of scanning electron microscopy is the capability for processing the image contrast, i.e., the image processing technique. Crewe et al were the first to apply this technique to a field emission scanning microscope and show images of individual atoms. They obtained a contrast which depended exclusively on the atomic numbers of specimen elements (Zcontrast), by displaying the images treated with the intensity ratio of elastically scattered to inelastically scattered electrons. The elastic scattering electrons were extracted by a solid detector and inelastic scattering electrons by an energy analyzer. We noted, however, that there is a possibility of the same contrast being obtained only by using an annular-type solid detector consisting of multiple concentric detector elements.


Author(s):  
C. W. Kischer

The morphology of the fibroblasts changes markedly as the healing period from burn wounds progresses, through development of the hypertrophic scar, to resolution of the scar by a self-limiting process of maturation or therapeutic resolution. In addition, hypertrophic scars contain an increased cell proliferation largely made up of fibroblasts. This tremendous population of fibroblasts seems congruous with the abundance of collagen and ground substance. The fine structure of these cells should reflect some aspects of the metabolic activity necessary for production of the scar, and might presage the stage of maturation.A comparison of the fine structure of the fibroblasts from normal skin, different scar types, and granulation tissue has been made by transmission (TEM) and scanning electron microscopy (SEM).


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